Chapter 4: Cell Structure and Function I. Cell Theory: 1. Every living thing is composed of one or more cells.2. The cell is the smallest/simplest unit of life.3. Under current conditions, all cells come from preexisting cells.

II. Prokaryotic Cells

A. Prokaryotic cells do contain DNA and ribosomes, but no membrane-bound organelles or nuclear membrane.

B. Include bacteria and archea (all unicellular).

C. Single strand of DNA.

Fig. 4.27a, p. 74

ribosomesIn cytoplasm

Prokaryotic Cell (Label)

III. Eukaryotic Cells

• Eukaryotic cells are characterized by the presence of membrane-bound organelles and a defined nucleus. Include animals, plants, fungi, and ‘protists.’

• Organelles: Discrete structures within eukaryotic cells with specific functions.

Nucleus

Brain of Cell. The nucleus is surrounded by two lipid bilayers, forming the nuclear envelope. The nuclear envelope has numerous pores, allowing certain items to leave the nucleus. The pores are not large enough to allow DNA to leave the nucleus. Also, the nucleus holds the nucleolus, which is responsible for making the components of the ribosomes.

Ribosomes

Construction Crew of Cell. Made of two pieces of RNA, the ribsomes read DNA and assemble amino acids into proteins.

+

Endoplasmic Reticulum

The UPS of the cell.

Rough ER contains ribosomes, so rough ER modifies proteins.

Smooth ER is involved with the modification of lipids rather than proteins.

Golgi Bodies

UPS/related to ER. Hollow tubes that are involved with processing of lipids and proteins. Golgi bodies produce vesicles (membrane-bound sacs) for shipment to specific locations within a cell.

Fig. 4.13, p. 64

DNA instructions forbuilding polypeptidechains leave the nucleusand enter the cytoplasm.

The chains (green) areassembled on ribosomesin the cytoplasm.

Important Vesicles

Lysosomes: Loaded with enzymes to digest cell components, or even entire cells.

Peroxisomes: Loaded with enzymes to break down fats and proteins.

Mitochondrion

Powerhouse. The mitochondrion is an organelle with a double membrane that functions to convert stored energy such as sugar into useable energy, ATP. Interestingly, the mitochondrion contains its own distinct DNA. Glucose to ATP.

Chloroplast

Solar Panel. The inner membrane hold pigments (such as chlorophyll) that collect light and the conversion to stored energy occurs within the membrane system. Solar energy is converted to stored chemical energy (glucose).

Plasma Membrane

The tails are fatty acid chains (hydrophobic) and the heads contain phosphate groups (hydrophilic). The basic function of the plasma membrane is to keep the contents within the membrane separate from the contents outside of the membrane.

A

B

C

Cytoskeleton

Made of microtubles (hollow tubes made of protein) and microfilaments (thin ‘ropes’ of twisting two polypeptide chains together).

Fig. 4.19, p. 69

tubulinsubunit

37nm

25nm

actinsubunit

onepolypeptidechain

8-12nm

Fig. 4.8a, p. 59

microtubules(components of cytoplasm)

Golgi body

vesicle

microfilaments(components of cytoskeleton)

mitochondrion

chloroplast

central vacuole

rough endoplasm reticulum (rough ER)

ribosomes (attached to rough ER)

ribosomes (free in cytoplasm)

smooth endoplasmic reticulum(smooth ER)

DNA + nucleoplasm

nucleolusnuclear envelope

NUCLEUS

plasma membrane

cell wall

Three Organelles Unique to Plants:

1.

2.

3.

Fig. 4.8b, p. 59

microfilaments

microtubules

components ofcytoskeleton

plasma membrane

mitochondrion

nuclear enevelope

nucleolus

DNA + nucleoplasm

NUCLEUS

vesicle

lysosome

rough ER

ribosomes(attached torough ERand free incytoplasm)

smooth ER

vesicle

Golgi body

pair ofcentrioles

IV. Cell Movement

A. Cytoskeleton can add/remove amino acids (important in mitosis).

B. Many extentions = cilia

C. Few extentions = flagellum

V. Cell Junctions

A. Tight Junction:

Cell connections don’t allow materials to flow past a surface. Proteins extend from the cell membranes of the neighboring cells, acting to bring the two cells close together

V. Cell Junctions

B. Adhering Junctions- Muscles cells are connected but also must be able to flex and stretch. They are connected with adhering junctions.

C. Gap Junctions - The nerve cells of your brain/nervous system have small gaps between connecting cells.